Variable phase shifter



D. R. AYER ET VARIABLE PHASE SHIFTER April 25; 1967 V 2 Sheets-Sheet 1Filed May 21, 1963 FIGB INVENTORS. DONALD R. AYER W. RALPH B'l' ATTORNEYApril 25; 1967 R, AYER ET AL 3,316,509

VARIABLE PHASE SHIFTER Filed May 21, 1963 2 Sheets-Sheet 2 b 45 78 40b62 38 I i I I I 420 4O 42G f i 45 INVENTORS H2 DONALD R. AYER w. RA F lG. 8 BY LOWE ATTORNEY United States Patent 3,316,509 VARIABLE PHASESHIFTER Donald R. Ayer and W. Ralph Lowe, Nashua, N.H., as-

signors to Sanders Associates, Inc., Nashua, N.H., a corporation ofDelaware Filed May 21, 1963, Ser. No. 282,012 10 Claims. (Cl. 33331)This invention relates to an improved high frequency variable phaseshifter and to an improved impedance matching device incorporating it.The phase shifter comprises a transmission line in which differentinsulators are longitudinally moved between inner and outer conductorsto vary the velocity of propagation and, accordingly, to vary the phasedelay imparted to signals propagating along the line. The phase shifterhas no sliding inner conductor contacts and is sufiiciently compact foruse in miniature high frequency circuits.

In general, a variable phase shifter is used to adjust the phase of ahigh frequency signal, or, in other words, to vary the time required fora signal to propagate between two points in a circuit. This can beaccomplished by changing either the physical length of the transmissionpath between the two points or the velocity of propagation along thepath. The velocity may be changed by varying the dielectric constant ofthe insulator between the transmission line inner and outer conductors.To obtain efiicient transfer of energy through a phase shifter, it isgenerally desirable that its characteristic impedance remainsubstantially unchanged when the phase delay through it is varied.

A common phase shifter used prior to the present invention is the linestretcher, a constant impedance transmission line constructed withtelescoping conductors so that the physical length of the transmissionpath can be varied. However, the trombone construction of the innerconductor requires sliding contacts; which are unreliable and costly toconstruct. In addition, line stretchers are not suited for compactconstruction are thus relatively incompatible with present compacttransmission line circuits incorporating strip transmission line or thelike.

Accordingly, it is an object of the present invention to provide animproved phase shifter having a small size.

Another object is to provide a small, constant impedance phase shifterthat is characterized by high reliability.

Still another object of the invention is to provide a compact phaseshifter having relatively simple and low cost construction.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combination of elements and arrangements of parts which will beexemplified in the construction hereinafter set forth and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a perspective view, partly broke away, of a phase shifterembodying the present invention,

FIG. 2 is a sectional view taken along line 22 of FIG. 1,

FIG. 3 is a top plan view, partly broken away, of another phase shifterembodying the invention.

A FIG. 4 is a sectional view taken along line 44 of FIG. 3,

FIG. 5 is a sectional view taken along line 5-5 of FIG. 3,

FIG. 6 is an enlarged view of a portion of FIG. 4,

FIG. 7 is a sectional view, partly broken away, of an impedance matchingdevice embodying the present invention; this view is taken along line7--7 of FIG. 8; and

FIG. 8 is a sectional view taken along line 88 of FIG. 7.

In general, the present phase shifter comprises a transmission line,having a fixed physical length, in which the dielectric material betweenthe inner and outer conductors is continuously changeable. The velocityof propagation in the phase shifter and, correspondingly, the phasedelay between its input and output ports, vary as the dielectricmaterial is changed. The phase shifter has no movable inner conductorcontacts, and accordingly, losses and impedance discontinuities arerendered substantially negligible so that reliable performance isachieved. Furthermore, it is compact, whether using coaxial or striptransmission line.

An improved impedance matching device utilizes the present phase shifterto adjust the electrical distance that an adjustable short circuitedstub is spaced from an impedance element being matched. This device,which is compact, is particularly suited for construction with striptransmission line.

More specifically, referring to FIGS. 1 and 2, the phase shifter ispreferably constructed with a conductor 10 provided with verticalportions 10a and 10b supported in a lower housing 12. A horizontalconductor portion 10c, extending within a cavity 14 in an upper housing16, links the portions 10a and 10b. The housings 12 and 16, made ofelectrical conducting material, such as aluminum or copper, form theouter conductors 17 of a transmission line of which conductor 10 is theinner conductor. A section 14a of the cavity 14 is partially filled withan insulator 18 having a high dielectric constant. Section 140,constituting the remainder of the cavity, may be filled with air, whoseunity dielectric constant is substantially lower than-that of theinsulator 18. The housing 16 is adapted to slide along the housing 12,in the directions indicated by the arrow 19, to change the length of theconductor portion 10c engaged by the insulator 18 and thereby change thephase delay imparted to signals propagating along the portion 100. Thelower housing 12, preferably an elongated rectangular bar, is formedwith cylindrical apertures 20 and 22 that accommodate the innerconductor portions 10a and 10b. Outer conductors 24a and 26a of coaxialconnectors indicated generally at 2-4 and 26 are secured to the housing12 and form extensions of the apertures 20 and 22. Inner conductor 10,shown having a circular cross section and an over-all U-shape, issymmetrically, disposed within the apertures 20 and 22 and the outerconductors 24a and 26a. The inner conductor can be supported withsuitable dielectric supports such as pins or beads (not shown) accordingto well-known techniques.

Still referring to FIGS. 1 and 2, the upper housing 16 is machined tofit over the lower housing 12 and has runners 28 that slidably engageways 30 on the housing 12 to guide the motion of the upper housing tothe longitudinal direction. Electrical contact between the housings maybe enhanced with spring contacts (not shown) or the like. I

As seen in FIG. 2, the cavity 14 preferably extends within the housing16 for at least twice the length L of the conductor portion 10c. Theinsulator 18, made of polytetrafluroethylene (commercially available asTeflon) or polyethylene, for example, substantially fills the cavitysection 14a for a length preferably slightly greater than L, leavingonly a narrow space 14c (FIG. 2) to allow movement of the housing 16 andthe insulator 18 along the inner conductor portion 100.

The characteristic impedance of a transmission line is an inversefunction of the dielectric constant of the insulator between theconductors and a direct function of the inner conductor thickness.

3 interconductor spacing, or, more specifically, the spacing between theinner and outer conductors relative to the in the cavity section 14a isgreater than in the section 14b, the interconductor spacing in portion14a should be correspondingly larger than the spacing in section 14b, tomaintain uniform impedance in both sections. This may be achieved bysecuring conducting strips 32 and 34 to the housing 16, in the section14b, to reduce the interconductor spacing. The insulator 18 and thestrips 32 and 34 have tapered ends 18a, 32a and 34a, respectively, toprovide a smooth electrical transition between the cavity sections 14aand 14b.

Referring to FIG. l, the phase shifter may conveniently have a scale 35engraved or stenciled on housing 12 and a pointer 36 secured to housing16 to indicate the position of the upper housing relative to the lowerhousing. The operation of the phase shifter of FIGS. 1 and 2 may beconsidered by assuming, for the purpose of illustration, that connector24 is an input port and connector 26 an output port. .Qualitatively, thevelocity of propagation along the inner conductor portion 100 is smallerin the cavity section 14a than in the section 14b, where the insulationbetween the conductor and the outer con-- ductors has a smallerdielectric constant. Accordingly, when the housing 16 is moved to theright (FIG. 1) so that the cavity portion 14a engages a larger portionof the conductor portion 100, the phase delay of signals arriving atconnector 26 increases with reference to the phase at the connector 24.

More specifically, assuming the length of the cavity 14 is at leastequal to 2L (i.e., at least twice the length of conductor portion 10c),let

' d =length of section 1401 enclosing conductor portion 10c,

d =length of section 14b enclosing conductor portion 100,

e =dielectric constant of insulator 18,

e =dielectric constant of insulator (e.-g., air) in section 14a, where ee and t=free space wavelength at the operating frequency.

Neglecting the fixed phase delay in the non-varying portions of thephase shifter, the relative phase delay, in radians,yalong the conductorportion 100 is given by when d =L. V

The range of phase delay, termed dynamic phase delay, is given by,

The dynamic phase delay can thus be increased by in- V creasing thelength of conductor portion 100 or by increasing the disparity betweenthe dielectric constants e and e 7 The inner, conductor 10 of the phaseshifter shown in FIGS. 1 and 2 can also be constructed with a strip lineconfiguration, as used in the devices. described below.

Since the dielectric constant A dual phase shifter, in which the phasedelays through two transmission lines indicated at 35 and 37 aresimultaneously varied inversely with respect to each other, is shown inFIGS. 3 thru 6. The lines 35 and 37, interconnecting ports 48 and 50 andports 52 and 54, respectively, have inner conductors 44 and 45,respectively. The dual phase shifter is constructed with a circularelectrically conducting housing 38 having an internal annular cavity 40(FIG. 4). A fiat outer ring 42, partially disposed within the cavity 40,supports an annular dielectric sheet 46 in a slot 42a (FIGS. 4 and 6).The sheet 46, in turn, carries the substantially semicircular striptransmission line inner conductors 4444 and the diametrically opposingconductor 45-45 on its inner edge.

. As best seen in FIGS. 4 and 5, cavity 40 has a narrow neck portion 40athat accommodates the ring 42 and an enlarged portion 40b in which theconductors 44 and 45 are disposed. Suitably seated bearings 56-56 in theportion 40a rotatably support the housing 38 on the ring 42 so that thehousing may be rotated withrespect to the ring. Insulators 58 and 60(FIG. 4), secured to the housing 38 in the cavity portion 40b, extendaround one half the circumference of the cavity. Conducting strips 62and 64 are secured to the housing 38 in the other half of the cavityportion 40b. The strips 62 and 64 and the cavity-forming walls of thehousing 38 are the outer conductors of the transmission lines 35 and 37.The portion of the cavity 40 containing the insulators 58 and 60 will bereferred to as a delay section.

Since the dielectric constant of the insulators 58 and 60 is larger thanthat of the air dielectric between the inner and outer conductorselsewhere in the transmission lines, the phase delays imparted tosignals propagated in the delay section are larger than elsewhere in thelines. Accordingly, the phase delay between the ports 48 and 50 is amaximum when the delay section fully engages the inner conductor 44.With the housing 38 rotated for this condition, the conductor 45 betweenthe ports 52 and 54, does not engage the insulators 58 and 60, and,hence, a minimum delay is imparted to signals propagating between latterports. Rotation of the housing 38 will now decrease the delay betweenthe ports 48 and 50 and increase the delay between the ports 52 and 54,as the delay section encloses less of the conductor 44 and more of theconductor 45.

More specifically, the phase delays, in radians, along the transmissionline inner conductors 44 and 45, respectively, are:

as g twa-vanwzauo (7) and where r is the radius of the circular pathalong which the conductors 44 and 45 are disposed,

k is the wavelength at the operating frequency,

0 is the angle between a reference line, indicated at 66 in FIG. 3, andone end of the transmission line delay section,

6 is the dielectric constant of the insulators 58 and 60,

in the delay section,

5 is the dielectric constant of the interconductor insulator (air) inthe rest of the cavity 40,

C is a constant, and

I The range of phase delay, AI the difference in the phase delay when0=0 and when 6=1r, or (approximately) is given by The differential phasedelay, or the difference in phase delay between the paired ports 48 and40, 52 and 54 for any value of 0, is given by The dual phase shifter issuited for automatic remote operation with a rotary actuator, such as anelectric motor (not shown), coupled to the housing 38 by means of holes6868 (FIGS. 3 and 4). The phase shifter may be supported, and ring 42constrained from rotation when the housing is rotated, by fastening thering 42 to a stationary base (not shown) with the aid of mounting holes70-70 (FIG. 3).

With further reference to FIGS. 3 thru 6, the inner conductors 44 and 45are preferably made of metallic foil bonded to the dielectric sheet 46according to standard strip transmission line techniques. The sheet 4 6and ring 42 may be fabricated in semicircular sections oined together inthe cavity 40, or the housing 38 may be formed from a pair of circularmembers fastened together with the sheet 46 and ring 42 between them.Wave- .guide-to-strip line transitions 7272, provided between each ofthe ports 48-54, and the inner conductors may take the form discussed onpages 4450 of the Handbook of T ri-Plate Components, Sanders Associates,Inc. (1956). The phase shifter can also be constructed with coaxial orstrip transmission line connectors at the ports 48-54.

The conductors 62 and 64 (FIG. 5) reduce the interconductor spacing tomaintain substantially uniform the characteristic impedance of thetransmission lines in the delay section and in other parts thereof. Inaddition, the insulators 58 and 60 and the conductors 62 and 64 arepreferably formed with tapered ends, similar to the ends 18a, 32c and34a (FIGS. 1 and 2) to provide smooth transitions at the ends of thedelay section. A scale, a portion of which is indicated in FIG. 3 at 74,may be provided on the ring 42, to coact with a pointer 76 secured tothe housing 38 for indication of the position of the delay section ofthe line with respect to the reference line 66 (FIG. 3). Spring contacts78-78 (FIGS. 4 and 5) are preferably provided between the inner edge ofthe ring 42 and the outer edge of the cavity portion 40b to providereliable electrical contact between the ring 42 and the housing 38.

Referring now to FIGS. 7 and 8, the phase shifter may be incorporated inan impedance matching device having an open-circuited transmission linestub indicated generally at 80. The stub 80 is connected in parallelwith a transmission line, indicated at 82, forming part of a phaseshifter generally similar to a single phase shifter in the dual deviceof FIG. 3. Variation of the phase delay along the stub 80 changes theimpedance presented by the stub to the line 82, and, in addition,adjustment of the phase shifter delay varies the electrical distance ofthe stub from one port of the matching device. Thus, the device providesan impedance whose phase and magnitude are variable over a wide range.

The impedance matching device has a base 84 with a metallic housing 86rotatably supported on it by bearings 88. A central shaft 90 issupported on the base 84 with bearings 92 for rotation independent ofthe housing 86. Arms 94 extend radially from the shaft 90 to move a stubassembly, indicated at 96 and described below in greater detail, in acircular path along the stub 80 as the shaft 90 is rotated.

The housing 86, preferably formed with a lower section 86a andan uppersection 86b, has a substantially annular interal cavity 98. As best seenin FIG. 8, the cavity has a plurality of concentric annular regions 98b,98c, 98d and 98e. The upper housing section is supported on the lowersection by two post sections 860 and 86d (FIG. 7) that interrupt theannular region 98c.

A dielectric disk 100, disposed within the cavity 98,

carries strip transmission line inner conductors 99 and 101 bonded toboth sides in the regions 98b and 98d form, respectively, the stub andthe line 82. The surfaces of the housing 86 forming the walls of thecavity regions 98b and 98d are the outer conductors for the stub 80 andthe transmission line 82. As seen in FIG. 7, the inner conductor 101 oftransmission line 82 extends in a generally semicircular path betweentwo strip line-to-wave-guide adapters, generally indicated at 102 and104, that include flanged waveguides 106 and 108, respectively.

As best seen in FIG. 8, the waveguides 106 and 108 are secured to thebase 84 and support the dielectric disk in a fixed position with respectto base 84. The disk 100 is held in place by insulators 110 disposedbetween inner conductor 101 and the waveguides 106 and 108. Additionalsupport for the disk 100 may be provided by dielectric members (notshown) that are slidably mounted between the disk and the housing 86 orthe stub control assembly 96.

Insulators 112 partially fill the cavity region 98d enclosing theconductor 101. More specifically, the insulators 112 occupysubstantially one-half the circumference of the region 98d, whileconducting members 114 partially fill the other half of thecircumference of this region. The construction of the cavity region 98d,insulators 112, conducting members 114 and the transmission line 82,between the flanged waveguides 104 and 106, is substantially similar tothe like parts of the rotary phase shifter described above withreference to FIGS. 3 thru 6. Thus, it provides a variable phase delaybetween the fianged waveguides when the housing 86 is rotated withrespect to the inner conductor 101. Similarly, rotation of the housing86 with respect to conductor 101 changes the electrical distance betweenthe stub and the flanged waveguide 106.

In addition, rotation of the shaft 90 moves the stub control assembly 96to change the electrical distance between the junction 116 (FIG. 7) ofthe stub 80 with the line 82 and the open circuit at the other end ofthe stub. This, in turn, changes the impedance presented by thetransmission line stub 80 to the line 82. For example, when theelectrical spacing of the open circuit from the junction 116 is aquarter wavelength, the impedance presented by the stub 80 to the line82 is, ideally, a short circuit, and when the spacing is a halfwavelength, the impedance is ideally an open circuit. At interme diatespacings the impedance varies between these values according towell-known principles. Thus, by rotating the shaft 90 and the housing86, the phase and magnitude of the impedance presented to waveguide 106can be independently selected.

Still referring to FIGS. 7 and 8, the stub assembly 96 may beconstructed as a toroid 120 of substantially rectangular cross sectionand having an annular slot 121 in its outer surface for receiving thedisk 100 and con ductors 99 of stub 80.

As best seen in FIG. 8, the toroid 120 has a conductive cylindricalinner portion 120a. Half of the circumference of the toroid outerportion, forming the slot 121, is formed with conductive semicircularmembers 122, symmetrically disposed above and below the disk 100.Similarly disposed dielectric semicircular members 123 form the otherhalf of the toroid outer portion.

The toroid 120 fits within the cavity region 98b of housing 86 and itsportion 120a, and conductive members 122 are constructed to maintainlow-reactance, sliding contact with the housing 86.

Rotation of shaft 90, revolving the entire stub assembly 96 to positionthe dielectric members 123 adjacent the full length of stub 80 innerconductor 99, provides maximum phase delay along the stub 80.Alternately, the assembly 96 can be rotated with respect to the disk 100to position the conductive members 122 adjacent the full length ofconductor 99 to provide minimum delay along 7 the stub. Thus, the stub.80 and the phase control assembly 96 operate to vary the phase delaybetween the junction 116 and the open circuited end of conductor 99 inthe same manner as each phase shifter in the dual device of FIG. 3.

The impedance matching device may be constructed, in the mannerdescribed, to have a small size and yet provide a wide range ofcontinuously adjustable complex impedances between the waveguides 106and 108. Thus, it is ideally suited for compensating for a wide range ofimpedance mismatches or, alternatively, for providing a desiredmismatch. Because of its small size, the matching device is particularlysuited for use with miniature high frequency circuits constructed withstrip transmission line or even miniature, high frequency, waveguide.

It.should be noted that even though the transmission line sections inFIGS. 7 and 8 do not include extensive direct electrical connectionsbetween the upper and lower ground plane surfaces, radiation into andout of the stub 80 and transmission line 82 can be kept at negligibleproportions. Specifically, if the housing sections 86a and 86b aresufficiently close together at the cavity portions 98c and 98e, andthese portions are sufiiciently Wide, the capacitive reactance betweenthe sections 86a and 86b will be negligible at the frequency ofoperation. Operation will then take place as if there were directelectrical connections. Similarly, the capacitance between the toroidportion 120a and the sections 86a and 86b 'minimizes imperfections inthe sliding contacts between these members.

The same principles apply to the embodiments of FIGS. 1-6. In thisconnection, reference is made to U.S. Patent No. 2,926,317.

It should be noted that the variable lengthlines and the impedancematching device described herein may be used to advantage as theadjustable components in tunable filters. For example, givenresonateline lengths corresponding to inductive and capactive'reactances, theywill resonate with and couple through capacitors incorporated in thestrip transmission lines. A series capacitor may take the compact formshown on pages 93 and 102 of Handbook of Tri-Plate Microwave Components,N. Wild et al., published by Sanders Associates, Inc., in 1956. Aparallel-connected capacitor may take the form of an enlargement of thewidthof the center conductor of the transmission line.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efiiciently attained and,since certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention, which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. A variable phase shifter for high frequency electric signals, saidphase shifter comprising, in combination,

:a transmission line having an inner conductor disposed within an outerconductor system, said inner conductor being the central portion of aloop having end portions connected to said central portion and angularlydisposed with respect thereto, one of said end portions serving as aninput terminal of said transmission line and the other of said endportions serving as an output terminal of said transmission line, firstand second insulators having different dielectric constants disposedwithin said trans- ,mission line between said inner conductor and saidouter conductor system and in tandem with each other, and means forchanging the relative lengths of said insulators disposed within saidtransmission line.

2. A variable phase shifter in accordance with claim 1 including meansfor moving said insulators longitudinally with respect to said innerconductor, the length of said inner conductor being less than thecombined length of said insulators.

3. A variable phase shifter in accordance with claim 1, including meansfor maintaining the impedance of said transmission line substantiallyuniform when either of said first and second insulators is disposedtherein.

4. .A variable phase shifter for high frequency electric signals, saidphase shifter comprising, in combination, a transmission line having aninner conductor disposed within an outer conductor system, said innerconductor being the central portion of a loop having end portionsconnected to said central portion and angularly disposed with respectthereto, one of said end portions serving as an input terminal to saidtransmission line and the other of said end portions serving as anoutput terminal of said transmission line, an elongated compositeinsulator comprising first and second sections having ditferentdielectric constants and arranged in end-to-end relationship, meanssupporting said insulator for movement into and along said transmissionline and between said inner conductor and said outer conductor system toinversely vary the length of said insulator sections disposed withinsaid transmission line, so as to cause a variation in phase between thesignals appearing on said input and output terminals.

5. The combination defined in claim 4 including a second transmissionline connected in parallel with said first transmission line and havingan inner conductor disposed within an outer conductor system, and meansfor varying the electrical length of said second transmission line.

6. A variable phase shifter for high frequency electric signals, saidphase'shifter comprising, in combination, first and second elongatedhousing members fitted to gether for longitudinal movement relative toeach other, said first member having a longitudinal recess opening onsaid second member, said second member having first and second aperturesthat communicate with said recess, said recess comprising first andsecond sections each of which extends along substantially one-half thelength thereof, a transmission line inner conductor extending along saidrecess for substantially one-half the length thereof with its endsextending into said apertures, the recess walls provided by said housingmembers constituting transmission line outer conductors for said innerconductor, a first insulator of relatively high dielectric constantsecured to said first member to occupy the space between said innerconductor and said outer conductors in said first section, a secondinsulator of relatively low dielectric constant occupying the spacebetween said inner and outer conductors in said second section, wherebyrelative movement of said members changes the length of said firstinsulator between said inner conductor and said outer conductors to varythe time delay imparted to signals propagating along said innerconductor between said first and second apertures.

7. The combination defined in claim 6 in which the spacing of said outerconductors from said inner conductor is greater in said first section ofsaid recess than in said second section thereof so that the impedance ofsaid transmission line remains constant during relative movement of saidmembers.

8. A high frequency rotary phase shifter comprising, in combination,housing means provided with an internal annular cavity having conductingwalls, a dielectric disk disposed in said cavity and mounted forrotation therein with respect to said housing means, said cavity wallsbeing the outer conductor for a strip transmission line that has a firststrip line inner conductor secured to said disk along a substantiallycircular path whose length is less than that of a full circle, saidfirst strip line inner conductor being the central portion of a loophaving first and second end portions connected to said central portionand angularly disposed with respect thereto, said first and second endportions effectively serving as input and output terminals,respectively, of said first strip transmission line, first and secondinsulators having different dielectric constants and arranged end-to-endin a circular path substantially adjacent said inner conductor path,said insulators being disposed in said cavity so that when said disk isrotated with respect to said housing means the lengths of said first andsecond insulators between said inner conductor and said cavity wallsvary inversely, thereby varying the time required for electric signalsto propagate along said inner conductor.

9. The combination defined in claim 8 in which said housing means has anannular slot communicating with said cavity, said first strip line innerconductor being secured to a first semicircular portion of said disk, asecond strip transmission line inner conductor secured to a secondsemicircular portion of said disk concentric with said first portion formovement along said first and second insulators when said disk isrotated with respect to said housing means, said second strip line innerconductor being the central portion of a loop having first and secondend portions connected to said central portion and angularly disposedwith respect thereto, said first and second end portions efiectivelyserving as input and output terminals, respectively, of said secondstrip transmission line, said end portions of said first and secondstrip transmission lines being connected to first and second pairs oftransmission line connecting means, respectively, said connecting meansbeing secured to said dielectric disk and being disposed outside of saidcavity, said combination thereby providing a dual phase shifting actionin which the phase delays imparted to signals propagating on said firstand second inner conductors between said pairs of connecting means varyinversely as said housing means is rotated with respect to saiddielectric disk.

10. The combination defined in claim 8 including a second striptransmission line inner conductor secured to said disk along asubstantially circular path and connected at one end thereof to saidfirst inner conductor, third and fourth insulators having diiferentdielectric constants and arranged end-to-end in a substantially circularpath adjacent the path of said second inner conductor, said third andfourth insulators being disposed in said cavity for rotation withrespect to said disk and said housing means to vary inversely thelengths of said third and fourth insulators between said second innerconductor and said cavity walls, thereby varying the time required forelectric signals to propagate along said second inner conductor.

References Cited by the Examiner UNITED STATES PATENTS 2,454,530 11/1948Tiley 333-31 3,017,587 1/1962 Kern et al. 333-31 3,092,793 6/1963Augustine et a1. 33331 3,192,492 6/1965 Linder 33331 ELI LIEBERMAN,Primary Examiner.

1. A VARIABLE PHASE SHIFTER FOR HIGH FREQUENCY ELECTRIC SIGNALS, SAIDPHASE SHIFTER COMPRISING, IN COMBINATION, A TRANSMISSION LINE HAVING ANINNER CONDUCTOR DISPOSED WITHIN AN OUTER CONDUCTOR SYSTEM, SAID INNERCONDUCTOR BEING THE CENTRAL PORTION OF A LOOP HAVING END PORTIONSCONNECTED TO SAID CENTRAL PORTION AND ANGULARLY DISPOSED WITH RESPECTTHERETO, ONE OF SAID END PORTIONS SERVING AS AN INPUT TERMINAL OF SAIDTRANSMISSION LINE AND THE OTHER OF SAID END PORTIONS SERVING AS ANOUTPUT TERMINAL OF SAID TRANSMISSION LINE, FIRST AND SECOND INSULATORSHAVING DIFFERENT DIELECTRIC CONSTANTS DISPOSED WITHIN SAID TRANSMISSIONLINE BETWEEN SAID INNER CONDUCTOR AND SAID OUTER CONDUCTOR SYSTEM AND INTANDEM WITH EACH OTHER, AND MEANS FOR CHANGING THE RELATIVE LENGTHS OFSAID INSULATORS DISPOSED WITHIN SAID TRANSMISSION LINE.